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United States Patent |
5,169,748
|
Apple
,   et al.
|
December 8, 1992
|
UV spectral sensitization
Abstract
A high resolution radiography system is presented utilizing a an
intensifying screen incorporating a UV emitting phosphor. The photographic
element exhibits enhanced sensitivity to the emission of the phosphor and
further comprises at least one compound selected from the group
comprising:
##STR1##
wherein R.sub.1 =substituted or unsubstituted aromatic ring; R.sub.2 =H,
substituted or unsubstituted alkyl or substituted or unsubstituted aryl;
R.sub.3 =an alkyl group, an aryl group, a COOR group wherein R is
hydrogen, alkyl, aryl or an alkali metal cation, HNR4+ wherein R.sub.4 is
alkyl, substituted alkyl or alkyaryl.
Inventors:
|
Apple; Bernard A. (Hendersonville, NC);
Fabricius; Dietrich M. (Hendersonville, NC);
Guy; Joseph T. (Hendersonville, NC)
|
Assignee:
|
E. I. Du Pont de Nemours and Company (Wilmington, DE)
|
Appl. No.:
|
788000 |
Filed:
|
November 7, 1991 |
Current U.S. Class: |
430/519; 430/139; 430/512; 430/567; 430/591; 430/966 |
Intern'l Class: |
G03C 001/06 |
Field of Search: |
430/512,519,139,966,567,591
|
References Cited
U.S. Patent Documents
4024069 | May., 1977 | Larach | 252/301.
|
4225653 | Sep., 1980 | Brixner | 428/690.
|
4246485 | Jan., 1981 | Bossomaier | 252/301.
|
4499159 | Feb., 1985 | Brines et al. | 430/966.
|
4654292 | Mar., 1987 | Oie et al. | 430/519.
|
4803150 | Feb., 1989 | Dickerson et al. | 430/502.
|
4855221 | Aug., 1989 | Factor et al. | 430/510.
|
4857446 | Aug., 1989 | Diehl et al. | 430/510.
|
4900652 | Feb., 1990 | Dickerson et al. | 430/507.
|
4940654 | Jul., 1990 | Diehl et al. | 430/522.
|
4948718 | Aug., 1990 | Factor et al. | 430/522.
|
4956269 | Sep., 1990 | Ikeda et al. | 430/519.
|
Foreign Patent Documents |
3217383 | Nov., 1982 | DE | 430/591.
|
0130285 | Mar., 1978 | DD | 430/519.
|
Primary Examiner: Bowers, Jr.; Charles L.
Assistant Examiner: Neville; Thomas R.
Claims
We claim as our invention:
1. A radiographic element comprising at least one x-ray intensifying screen
in operative association with a photographic element;
wherein said x-ray intensifying screen comprises:
a support bearing a phosphor layer thereon; said phosphor layer comprises a
binder with a phosphor dispersed therein, said phosphor further
characterized by emission of light thereof wherein at least 80% of light
emitted upon exposure to x-ray radiation is between 300 and 390 nm, and
said binder absorbs less than 10% of any light emitted from said phosphor;
wherein said photographic element comprises:
a substrate with at least one hydrophilic colloid layer coated thereon
wherein said hydrophilic colloid layer contains photosensensitive silver
halide grains, wherein at least 50% of said silver halide grains comprise
tabular grains with an average aspect ratio of greater than 2:1; said
colloid layer further contains at least one compound selected from the
group comprising:
##STR6##
wherein R1=substituted or unsubstituted aromatic ring; R2=H, substituted
or unsubstituted alkyl or substituted or unsubstituted aryl; R3=an alkyl
group, an aryl group, a COOR group wherein R is hydrogen, alkyl, aryl or
an alkali metal cation, HNR4+ wherein R4 is alkyl, substituted alkyl or
alkyaryl.
2. A radiographic element as recited in claim 1 wherein said phosphor has a
peak emission between 310 and 360 nm.
3. A radiographic element as recited in claim 1 wherein said phosphor is
selected from the group comprising yttrium tantalate, yttrium tantalate
activated with gadolinium, and lanthanum oxybromide activated with
gadolinium.
4. A radiographic element as recited in claim 1 wherein said binder
comprises an acrylic resin with an average molecular weight of about
100,000 to about 300,000.
5. A radiographic element as recited in claim 1 wherein said silver halide
grain is taken from the group consisting of silver bromide, silver
chloride, silver iodide or mixtures thereof.
6. a radiographic element as recited in claim 1 wherein said compound is
selected from the group consisting of
##STR7##
7. A radiographic element as recited in claim 1 wherein 0.05 to 15 mmoles
of said compound are present per mole of silver.
8. A radiographic element as recited in claim 7 wherein 0.10 to 2 mmoles of
said compound are present per mole of silver.
Description
FIELD OF INVENTION
This invention relates to the formation of a radiographic image. More
specifically this invention relates to improvements in radiographic images
formed with an intensifying screen. Still more specifically, this
invention relates to improvements in sensitization of radiographic film
for use with ultraviolet emitting intensifying screens.
BACKGROUND OF THE INVENTION
Radiography has been employed for many years as a medical diagnostic tool.
A subject to be studied is placed between a x-ray radiation source and a
detection system which typically includes an intensifying screen and a
suitable photographic film. Intensifying screens have been employed in the
art as a conversion device wherein x-ray radiation is converted to lower
energy radiation such as visible radiation. Photographic film captures the
image emitted by the intensifying screen and with subsequent development
of the photographic film an image is generated which represents the
variations in absorption of x-ray radiation as it passed through the
subject.
Subject dosage and image quality are typically directly related for a given
film/screen combination. There is an ongoing need to improve the image
quality without increasing overall dosage for the subject. The dilemma has
been advanced substantially by the use of both sensitizing and acutance
dyes within the photographic element.
Sensitizing dyes are known in the art as a means for increasing the
sensitivity of a silver halide emulsion to a specific band of wavelengths.
A myriad of dyes have been presented to the art field as exemplified in
Research Disclosure, No 308, December, 1989, Item 308119. In the field of
radiography the spectral response of the silver halide emulsion preferably
corresponds to the blue or green emission of the intensifying screen.
Acutance dyes have been presented in the art as a means of greatly
improving image quality with subsequent minor increase in subject dose.
This improved image quality is accomplished by decreasing the amount of
light which scatters within the emulsion and more importantly by
decreasing the amount of cross-over. Cross-over typically refers to screen
emission which passes through, and is scattered by, the closest emulsion
and the substrate and is subsequently captured by the emulsion on the
opposite side of the support. The scattering of the emission as it passes
through the support decreases the resolution of the resulting image.
Pyrazolone dyes have shown great utility as crossover dyes as exemplified
in U.S. Pat. Nos. 4,900,652; 4,948,718; 4,803,150; 4,855,221; 4,940,654
and 4,857,446.
In general, acutance or cross-over dyes compete with the silver halide
grains for available emission from the intensifying screen resulting in a
loss of overall photographic speed. The practitioner of the art is
therefore forced to reach a balance between the photographic speed and
resolution for a particular application.
Recent advances in the art include the use of intensifying screens which
are comprised of phosphors which emit in the ultraviolet. One advantage of
systems utilizing these phosphors is the inherent UV absorption of the
photographic supports typically employed in the art. Cross-over is reduced
substantially without the use of dyes and, in fact, one practicing the art
would prefer to exclude acutance dyes in a system utilizing UV emitting
screens. The resolution obtained with UV intensifying screens typically
far exceeds the prior art techniques which employ acutance dyes and
conventional intensifying screens. Further improvements with dyes are not
expected to be warranted and, in fact, would be considered to be
detrimental in light of the expected loss in system speed.
Contrary to these teachings from the art is a dye family which is well
known in the art as an acutance dye, yet when utilized within the
teachings provided herein has the unexpected property of increasing the
system speed in the ultraviolet. Therefore, instead of decreasing system
speed with a corresponding improved resolution as observed with blue and
green emitting phosphors, films containing these dyes actually demonstrate
an increased speed at a comparable resolution. An increase in speed is
observed in spite of the lack of ultraviolet absorption by the dye.
SUMMARY OF THE INVENTION
Improved spectral sensitization of a silver halide photographic emulsion
and other improvements are provided in a radiographic element comprising
at least one x-ray intensifying screen in operative association with a
photographic element;
wherein said x-ray intensifying screen comprises:
a support bearing a phosphor layer thereon; said phosphor layer comprises a
binder with a phosphor dispersed therein, said phosphor further
characterized by emission of light thereof wherein at least 80% of the
light emitted upon exposure to x-ray radiation is between 300 and 390 nm,
and said binder absorbs less than 10% of any light emitted from said
phosphor;
wherein said photographic element comprises:
a substrate with at least one hydrophilic colloid layer coated thereon
wherein said hydrophilic colloid layer contains photosensitive silver
halide grains, wherein at least 50% of said silver halide grains comprise
tabular grains with an average aspect ratio of greater than 2:1; said
colloid layer further contains at least one compound selected from the
group comprising:
##STR2##
wherein R1=substituted or unsubstituted aromatic ring; R2=H, substituted
or unsubstituted alkyl or substituted or unsubstituted aryl; R3=a alkyl
group, a aryl group, a COOR group wherein R is hydrogen, alkyl or aryl,
alkali metal cation, HNR4+ wherein R4 is alkyl, substituted alkyl or
alkyaryl.
DETAILED DESCRIPTION OF THE INVENTION
A class of pyrazolone azo dyes incorporated in a silver halide emulsion
according to the teachings of this invention increase the speed of the
silver halide grains contained therein when exposed with ultraviolet
radiation. The dye structures useful within the ambit of this invention
are:
##STR3##
wherein R1=substituted or unsubstituted aromatic ring; R2=H, substituted
alkyl, unsubstituted alkyl, substituted aryl, or unsubstituted aryl; R3=an
alkyl group, an aryl group, a COOR group wherein R is hydrogen, alkyl, aryl
or an alkali metal cation, HNR4+ wherein R4 is alkyl, substituted alkyl or
alkyaryl. The exemplary examples provided below are known in the art as
acutance dyes when employed with conventional blue or green emitting
screens. When ultraviolet emitting screens are used these dyes show great
utility as a sensitizer within the teachings of this invention. The
exemplary examples listed below are not intended to limit the bounds of
the described invention in any way:
##STR4##
These dyes may be dissolved in any of a host of suitable solvents including
water, basic water, methanol, ethanol and others as known in the art. The
solutions containing these dyes are added to a photographic emulsion as
known in the art in an amount in the range of 0.05 to 15 mmoles of dye per
mole of silver and most preferably in an amount in the range of 0.10 to 2
mmoles of dye per mole of silver. The time and rate of addition are not
important, however, we prefer addition after completion of chemical
sensitization.
Representative comparative cross-over dyes which do not exhibit the
unexpected increase in UV speed are:
##STR5##
There are many well-known X-ray phosphors which emit in the ultraviolet
when exposed to x-ray radiation. These phosphors are also known to produce
improved image quality. However, it is also well-known that x-ray
intensifying screens prepared from these UV emitting phosphors, have low
contrast and depressed maximum density (Dmax) therefore causing a speed
decrease and thus increased patient dosage must be employed. This dosage
is deleterious to patient health and it has not been conventional in the
prior art to employ these UV emitting screens with conventional medical
x-ray films. Typical of these UV emitting phosphors are, for example
YTaO.sub.4 either alone or activated with gadolinium, bismuth, lead,
cerium or mixtures of these activators; LaOBr activated with gadolinium or
gadolinium and thulium; and La.sub.2 O.sub.2 activated with gadolinium,
among others. Most of these phosphors emit mainly in the UV (e.g. 300 to
390 nm, for example), although some small amount of visible light (e.g. up
to 20% and preferably less than 10%) may also be emitted therefrom.
For the purpose of this invention, UV emitting phosphors will emit in the
range of 300 to 390 nm and preferably in the range of 310 to 360 nm. For
the phosphors of this invention to be applicable in practical X-ray
imaging systems, the conversion efficiency of the phosphor, i.e. the
efficiency with which the energy carried by an X-ray quantum is absorbed
by this phosphor, and is then converted to light photons emitted by the
phosphor, should be higher than 5%.
These phosphors may be prepared as is well-known in the prior art and then
mixed with a suitable binder before coating on a suitable support. Once
prepared in this manner, this element is conventionally known as an x-ray
intensifying screen and is eminently suitable for radiological
evaluations.
There are a host of commercially available X-ray intensifying phosphors
that do not function within the metes and bounds of this invention. These
include the following:
______________________________________
Peak
Phosphor Emission (nm)
Remarks
______________________________________
Calcium Tungstate
410 Not a UV phosphor
YTaO4:Nb 400 Not a UV phosphor
Gd2O2S:Tb 520 Not a UV phosphor
YTaO4:Tm 335 More than 20% in
the
visible
BaFX:Eu (X = halide)
380 More than 20 in
the
visible
LaOBr:Tm 370 & 470 Double Peak - not a
UV phosphor
______________________________________
Conventionally, a intensifying screen comprises a support, an intensifying
phosphor layer, and a topcoat or protective layer thereon. A reflective
layer, such as a whitener (e.g. TiO2 dispersed in a suitable binder) may
also be added into the screen structure. Commonly, this reflective layer
is interposed between the phosphor layer and the support, or,
alternatively, the whitener may be dispersed directly into the support.
The reflective layer generally increases the light output of the
intensifying screen during use. The protective layer is important to
protect the phosphor layer against mechanical damage. The protective layer
should generally also be UV transparent so that the flow of UV light from
the phosphor is not decreased. Those layers that are known to absorb a
great deal of UV light (e.g. polyethylene terephthalate films, for
example) are not particularly useful within this invention. In operation,
the intensifying screen absorbs x-rays that impinge thereon and emits
energy having a wavelength that is readily captured by the photographic
silver halide x-ray film associated therewith. Recently, an effective
x-ray intensifying phosphor based on yttrium, gadolinium or lutetium
tantalate has been introduced. This particular phosphor, which has the
monoclinic M' phase, is particularly effective in capturing x-rays. Some
of these tantalate phosphors are also efficient emitters of UV light and
are particularly preferred within the metes and bounds of this invention.
They are generally prepared according to the methods of Brixner, U.S. Pat.
No. 4,225,653, and the information contained in this reference is
incorporated herein by reference thereto. The phosphors of this invention,
which cannot emit no less than 80% of their light below 300 nm or above 390
nm, are generally manufactured by mixing the various oxides and firing in a
suitable flux at elevated temperatures. After firing, pulverizing and
washing, the phosphor is mixed with a suitable binder in the presence of a
suitable solvent therefor and coated on a support, with the proviso that
said binder can absorb less than 10% of any UV light emitted from said
phosphor. All of these steps are described in the aforementioned Brixner
reference and all are well-known in the prior art. A protective topcoat
may also be applied over this phosphor coating, in fact it is preferred.
In a particularly preferred embodiment, a x-ray intensifying screens is
made by dispersing YTaO4 phosphor made as described above, in a mixture of
acrylic resins using a solvent. This mixture is then coated on a
polyethylene terephthalate support containing a small amount of anatase
TiO2 whitener dispersed therein. The phosphor may be coated to a coating
weight of ca. 15 to 100 mg of phosphor per cm2. A topcoat of
styrene/acrylonitrile copolymer is coated thereon and dried.
In the radiological process, it is conventional to employ a photosensitive
silver halide film element with the above described X-ray intensifying
screens. In the practice of this invention, the silver halide element will
be comprised of silver halide grains. These element are also well-known in
the prior art and the preparation of grains are also known and taught
therein. The grains are generally made into an emulsion using a binder
such as gelatin, and are sensitized with gold and sulfur, for example.
Other adjuvants such as antifoggants, wetting and coating aides, other
sensitizing dyes, hardeners etc. may also be present if necessary. The
emulsion may be double-side coated on the support and a thin, hardened
gelatin overcoat is usually applied over each of the emulsion layers to
provide protection thereto. Since the emulsions useful within the ambit of
this invention are generally UV sensitive in and of themselves, dyes in
addition to those taught herein may not be required. However, if required,
a small amount of a sensitizing dye might advantageously be added.
Additionally, it is also conventional to add a sensitizing dye to tabular
emulsions in order to increase their ability to respond to light.
The silver halide emulsion may employ any of the conventional halides but
preferred are pure silver bromide or silver bromide with small amounts of
iodide incorporated therein (e.g. 98% Br and 2% I by weight for example).
Any grain morphology is suitable for demonstration of these teachings
including, but not limited to, grains which are formed by splash
techniques and those formed by techniques involving spray techniques (i.e.
single and double jet procedures). Tabular grains are most preferred.
Tabular grain silver halide products are well-known in the prior art with
exemplary methods of manufacture described by Maskasky in U.S. Pat. Nos.
4,400,463; Wey, 4,399,205; Dickerson, 4,414,304; Wilgus et al., 4,434,226;
Kofron et al., 4,439,520; Nottorf, 4,722,886; and Ellis, 4,801,522.
After the grains are made, it is usually preferable to disperse the grains
with a binder (e.g. gelatin or other well-known binders such as polyvinyl
alcohol, phthalated gelatins, etc.). In place of gelatin other natural or
synthetic water-permeable organic colloid binding agents can be used as a
total or partial replacement thereof. Such agents include water permeable
or water-soluble polyvinyl alcohol and its derivatives, e.g., partially
hydrolyzed polyvinyl acetates, polyvinyl ethers, and acetals containing a
large number of extralinear --CH2HOH-- groups; hydrolyzed interpolymers of
vinyl acetate and unsaturated addition polymerizable compounds such as
maleic anhydride, acrylic and methacrylic acid ethyl esters, and styrene.
Suitable colloids of the last mentioned typed are disclosed in U.S. Pat.
Nos. 2,276,322, 2,276,323 and 2,347,811. The useful polyvinyl acetals
include polyvinyl acetalaldehyde acetal, polyvinyl butyraldehyde acetal
and polyvinyl sodium o-sulfobinzaldehyde acetal. Other useful colloid
binding agents include the poly-N-vinyllactams of Bolton U.S. Pat. No.
2,495,918, the hydrophylic copolymers of N-acrylamido alkyl betaines
described in Shacklett U.S. Pat. No. 2,833,650 and hydrophilic cellulose
ethers and esters. Phthalated gelatins may also be used as well as binder
adjuvants useful for increasing covering power such as dextran or the
modified, hydrolysed gelatins of Rakoczy, U.S. Pat. No. 3,778,278.
It is most preferable to chemically sensitize the grain with salts that are
well known in the art. The most common sensitizers are salts of gold or
sulfur. Sulfur sensitizers include those which contain labile sulfur, e.g.
allyl isothiocyanate, allyl diethyl thiourea, phenyl isothiocyanate and
sodium thiosulfate for example. Other non-optical sensitizers such as
amines as taught by Staud et al., U.S. Pat. No. 1,925,508 and Chambers et
al., U.S. Pat. No. 3,026,203, and metal salts as taught by Baldsiefen,
U.S. Pat. No. 2,540,086 may also be used.
The emulsions can contain antifoggants, e.g. 6-nitrobenzimidazole,
benzotriazole, triazaindenes, etc., as well as the usual hardeners, i.e.,
chrome alum, formaldehyde, dimethylol urea, mucochloric acid, and others
are recited in Research Disclosure, No. 308, December 1989, Item 30819.
Other emulsion adjuvants that may be added comprise matting agents,
plasticizers, toners, optical brightening agents, surfactants, image color
modifiers, non-halation dyes, and covering power adjuvants among others.
The film support for the emulsion layers used in the process may be any
suitable transparent plastic. For example, the cellulosic supports, e.g.
cellulose acetate, cellulose triacetate, cellulose mixed esters, etc. may
be used. Polymerized vinyl compounds, e.g., copolymerized vinyl acetate
and vinyl chloride, polystyrene, and polymerized acrylates may also be
mentioned. Preferred films include those formed from the
polyesterification product of a dicarboxylic acid and a dihydric alcohol
made according to the teachings of Alles, U.S. Pat. No. 2,779,684 and the
patents referred to in the specification thereof. Other suitable supports
are the polyethylene terephthalate/isophthalates of British Patent 766,290
and Canadian Patent 562,672 and those obtainable by condensing terephthalic
acid and dimethyl terephthalate with propylene glycol, diethylene glycol,
tetramethylene glycol or cyclohexane 1,4-dimethanol (hexahydro-p-xylene
alcohol). The films of Bauer et al., U.S. Pat. No. 3,052,543 may also be
used. The above polyester films are particularly suitable because of their
dimensional stability.
When polyethylene terephthalate is manufactured for use as a photographic
support, the polymer is cast as a film, the mixed polymer subbing
composition of Rawlins, U.S. Pat. No. 3,567,452 is applied and the
structure is then biaxially stretched, followed by application of a
gelatin subbing layer. Alternatively, antistatic layers can be
incorporated as illustrated, for example, by Miller, U.S. Pat. Nos.
4,916,011 and 4,701,403, Cho, U.S. Pat. Nos. 4,891,308 and 4,585,730 and
Schadt, U.S. Pat. No. 4,225,665. Upon completion of stretching and
application of subbing composition, it is necessary to remove strain and
tension in the base by a heat treatment comparable to the annealing of
glass.
The emulsions may be coated on the supports mentioned above as a single
layer or multi-layer element. For medical x-ray applications, for example,
layers may be coated on both sides of the support which conventionally
contains a dye to impart a blue tint thereto. Contigous to the emulsion
layers it is conventional, and preferable, to apply a thin stratum of
hardened gelatin supra to said emulsion to provide protection thereto.
The dyes taught herein are commercially available. Alternatively, standard
synthetic procedure can be used to manufacture the compounds of the
current invention. The following specific examples are provided as
reference and are not intended to limit the claims in any way.
This invention will now be illustrated by the following specific example
which is not intended to limit the claims in any way.
EXEMPLARY DYE SYNTHESIS EXAMPLES
Synthesis of Dye 1-3
Fifty ml of concentrated HCl was diluted with 125 ml water and mixed with
28.8 g 4-aminobenzoic acid, sodium salt. The resulting mixture was cooled
to 0.degree. C. before adding 12.5 g sodium nitrite dissolved in 25 ml
water. The addition rate was controlled to maintain a reaction temperature
below 5.degree. C. The resulting slurry of precipitated diazonium salt and
water was treated with urea until potassium iodide paper tested negative
(no color). 4-(3-Methyl-5-oxo-2-pyrazolin-1-yl) -benzoic acid, 38.5 g, was
slurried with 250 ml of water. After cooling to 0.degree. C., 50 g sodium
hydroxide in 150 ml of water was added. The resulting solution was stirred
and cooled to <5.degree. C. while adding the diazonium salt slurry
dropwise. When addition of diazonium salt was complete, the ice bath was
removed and the reaction mixture allowed to warm to room temperature. The
mixture was acidified and the precipitated dye collected by filtration.
After washing successively with dilute HCl and water, the dye was dried to
yield 61.08 g, mp 327.degree.-328.degree. C., .lambda..sub.max =395
(.epsilon.=28,000), 275 (.epsilon.=23,000).
Synthesis of Dye 1-4
Ten ml of concentrated HCl was diluted with 25 ml water and mixed with 5.19
g sulfanilic acid. The resulting mixture was cooled to 0.degree. C. before
adding 2.1 g sodium nitrite dissolved in 5 ml water. The addition rate was
controlled to maintain a reaction temperature below 5.degree. C. The
resulting slurry of precipitated diazonium salt and water was treated with
urea until potassium iodide paper tested negative (no color).
4-(3-Methyl-5-oxo-2-pyrazolin-1-yl)-benzoic acid, 3.78 g, was slurried
with 50 ml of water. After cooling to 0.degree. C., 10 g sodium hydroxide
in 30 ml of water was added. The resulting solution was stirred and cooled
to <5.degree. C. while adding the diazonium salt slurry dropwise. When
addition of diazonium salt was complete, the ice bath was removed and the
reaction mixture allowed to warm and stir at room temperature for one
hour. The mixture was acidified and the precipitated dye collected by
filtration. After washing with acetone and drying, the yield was 6.12 g,
mp 333.degree. C., .lambda..sub.max =390 (.epsilon.=24,000), 275
(.epsilon.=18,000).
EXAMPLE SCREEN A
An X-ray intensifying screen structure was made using the following
procedures:
A. The Binder Solution
The following ingredients were prepared:
______________________________________
Ingredient Amount (g)
______________________________________
n-Butyl acetate 43.13
n-Propanol 34.00
Carboset 525 (1) 10.00
Carboset 526 (2) 10.00
Polymeric organic
0.07
silicone fluid
Zelec 2457E (3) 0.40
Aerosol OT-100 (4)
0.40
Pluronic 31R1 (5)
2.00
______________________________________
(1) Acrylic resin; ave. mol. wt. 260,000; acid no. 76-85; B. F. Goodrich
Co., Cleveland, OH
(2) Acrylic resin; ave. mol. wt. 200,000; acid no. 100; B.F. Goodrich Co.,
Cleveland OH
(3) Anionic antistatic agent of mixed mono and dialkylphosphates of the
general structure R2HPO4, where R is C8 to C10 alkyl; E.I. du Pont de
Nemours & Co., Wilmington, DE
(4) Sodium dioctyl sulfosuccinate per U.S. Pat. No. 2,441,341
(5) Ethylene oxide/propylene oxide block copolymer; ave. mol. wt. 3200;
BASF Wyandotte; Wyandotte, MI
B. The X-ray Phosphor
The following ingredients were thoroughly mixed in a paint shaker for about
2 hours before charging to a alumina crucible:
______________________________________
Ingredient Amount (g)
______________________________________
Y2O3 101.46
Ta2O5 198.54
Li2SO4 150.00
______________________________________
The crucible was then placed in a standard, commerical, high temperature
furnace and fired at about 1200.degree. C. for about 8 hours and then at
about 1250.degree. C. for about 16 hours. The furnace was then allowed to
cool and the contents of the crucible weighed and washed thoroughly with
water to remove the unreacted salts and flux. This material was then added
to the binder from above using about 200 g of phosphor/60 g of binder
solution. This material was placed in a plastic container along with about
85 g of 3.8 in. diameter corundum balls (ca. 15 balls) and this mixture was
then ball milled for about 12 to 16 hours at room temperature with a
rotation speed of about 60 rpm. After this step, the ball milled
suspension was filtered through a 75 mesh Nylon bag and coated onto a
suitable support.
The support used was 0.010 inch thick, dimensionally stable polyethylene
terephthalate film containing a small amount of a whitener (e.g., anatase
TiO2) dispersed therein. This whitener will give the support some opacity
to visible light (e.g. optical density of ca.>1.7). The coating weight of
the phosphor dispersion placed thereon was about 100 mg of phosphor per
cm2.
C. The Overcoat Layer
An overcoat layer is prepared from the following solutions:
______________________________________
1) Ingredient Amount (g)
______________________________________
Acetone 67.00
Methanol 9.00
n-Butyl acetate 4.80
Tyril* 100 (1) 12.70
Carboset* XL-27 (2)
9.00
______________________________________
(1) Styrene/acrylonitrile copolymer resin; Dow Chemical Co., Midland, MI
(2) Acrylic resin; ave. mol. wt. 30,000; acid no. 80, B.F. Goodrich Co.,
Cleveland, OH
A gel solution is prepared by mixing the following ingredients until a
thick gel forms:
______________________________________
Ingredient Amount (g)
______________________________________
2) Methanol 14.70
Triamylamine 0.20
Carbopol* 1342 (1)
0.132
3) Solution 1 50.00
Gel Solution 2
12.19
______________________________________
(1) Acrylic resin thickener; B. F. Goodrich Co., Cleveland, OH This
solution is filtered and a mixture is prepared as follows:
This mixture is coated on top of the phosphor coating using a doctor knife
with a 0.004 in. gap. The resulting top-coat is air dried for 12-16 h at
40.degree. C.
EXAMPLE OF PREPARATION FOR THE FILM ELEMENT E-1
A conventional, tabular grain, blue sensitive X-ray emulsion was prepared
as well-known to one of normal skill in the art. This emulsion had tabular
silver bromide grains. After precipitation of the grains the average aspect
ratio was determined to be about 5:1 and thickness of about 0.2 um. The
procedures for making tabular grains of this nature are fully described in
Nottorf, U.S. Pat. No. 4,772,886 and Ellis, U.S. Pat. No. 4,801,522, the
contents of which are incorporated herein by reference.
These grains were dispersed in photographic grade gelatin (about 117 grams
gelatin/mole of silver bromide) and a solution of 200 mg of
5-(3-methyl-2-benzothiazolinylidene)-3-carboxymethylrhodanine sensitizing
dye dissolved with 128 mg of tri-n-butylamine and 2 ml of methanol added
to achieve 133 mg of dye per mole of silver halide. At this point, the
emulsion was brought to its optimum sensitivity with gold and sulfur salts
as is well-known to those skilled in the art. The emulsion was then
stabilized by the addition of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene
and 1-phenyl-5-mercaptotetrazole. A large sample of the stock emulsion was
divided into smaller samples containing 0.15 moles of silver halide.
Immediately after cessation of sensitization the subject dyes were added
as a water solution in the amounts indicated in the Table. Control samples
were prepared in a manner identical to the inventive examples. The usual
wetting agents, antifoggants, coating aides and hardeners were added and
this emulsion was then coated on a dimensionally stable, 7 mil
polyethylene terephthalate film support which had first been coated with a
conventional resin sub followed by a thin substratum of hardened gelatin
applied supra thereto. These subbing layers were present on both sides of
the support. The emulsion was coated on one side of the support at a
silver halide coating weight of about 2 g/m2. A thin abrasion layer of
hardened gelatin was applied over each of the emulsion layers. After
drying, samples of this film were used with X-ray intensifying screens as
further described herein.
PREPARATION FOR THE FILM ELEMENT
A conventional blue sensitive X-ray emulsion was prepared as well-known to
one of normal skill in the art. This emulsion had conventional silver
bromide grains. These grains were dispersed in about 107 grams of
photographic grade gelatin per mole of silver bromide. The emulsion was
brought to its optimum sensitivity with gold and sulfur salts as is
well-known to those skilled in the art. The emulsion was then stabilized
by the addition of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene and
1-phenyl-5-mercaptotetrazole. After cessation of sensitization the subject
dyes were added as a water solution in the amounts indicated in the Table.
Control samples were prepared in a manner identical to the inventive
examples. The usual wetting agents, antifoggants, coating aides and
hardeners were added and this emulsion was then coated on a dimensionally
stable, 7 mil polyethylene terephthalate film support which had first been
coated with a conventional resin sub followed by a thin substratum of
hardened gelatin applied supra thereto. These subbing layers were present
on both sides of the support. The emulsion was coated on one side of the
support at a silver halide coating weight of about 2.5 g/m2. A thin
abrasion layer of hardened gelatin was applied over each of the emulsion
layers. After drying, samples of this film were used with X-ray
intensifying screens as further described herein.
FILM/SCREEN EXPOSURE EXAMPLE
Screens were used to expose X-ray film elements. Screens made according to
the above description were used and are represented by Screen A. Control
Screen B was a standard LaOBr:Tm screen which is commercially available
from DuPont (Wilmington, Del.). The screens were given an exposure to a 60
KvP X-ray source with a tungsten cathode. After exposure, the films were
developed in a standard X-ray developer formulation, fixed, washed and
dried as known in the art.
TABLE 1
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RELATIVE PHOTOGRAPHIC SPEEDS
AMOUNT
EMUL- OF DYE RELATIVE SPEED
SION DYE g/mole Ag SCREEN A SCREEN B
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E-1 -- 0 100 100
E-1 C-3 0.5 93 92
E-1 C-4 0.5 25 26
E-1 I-1 0.13 110 97
E-1 I-1 0.33 104 89
E-1 I-1 0.53 108 86
E-1 I-2 0.25 99 96
E-1 I-2 0.50 106 98
E-1 I-2 0.75 108 96
E-1 I-3 0.07 105 100
E-1 I-3 0.13 100 102
E-1 I-3 0.33 93 85
E-1 I-4 0.80 102 90
E-1 I-4 1.07 105 78
E-1 I-4 1.33 109 --
E-2 -- 0 100 100
E-2 I-1 0.13 105 99
E-2 I-1 0.27 103 94
E-2 I-1 0.53 90 80
E-2 I-1 0.67 87 79
E-2 I-1 0.80 88 74
E-2 I-1 0.93 88 71
E-2 I-3 0.05 96 99
E-2 I-3 0.09 90 88
E-2 I-3 0.19 94 89
E-2 I-3 0.37 93 85
E-2 I-3 0.47 95 87
E-2 I-4 0.05 100 99
E-2 I-4 0.09 90 92
E-2 I-4 0.19 93 92
E-2 I-4 0.37 91 90
E-2 I-4 0.47 93 87
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